1. Field of the Invention
The present invention relates to a lens apparatus and, more specifically, to a lens apparatus having vapor-resistant ventilation and an optical instrument using such a lens apparatus.
2. Description of the Related Art
Heretofore, in lens-barrels (lens apparatuses) having a zoom mechanism, there have been many cases wherein when a lens-holding frame holding a lens or a lens group arranged on the utmost object side moves (changes the overall length of the lens barrel) during a zooming operation, an air volume within the lens-barrel changes. When an internal volume of the lens-barrel changes, by ventilation through a clearance of the lens-barrel, air comes in and out so that the pressure in the lens-barrel is maintained substantially equal with the external pressure, enabling the lens-holding frame to be smoothly moved.
On the other hand, in providing vapor-resistant performance in such a lens-barrel, air cannot come in and out because the lens-barrel is hermetically sealed relative to the exterior environment. Several techniques are disclosed in Japanese Patent Publication No.2909906, Japanese Patent Laid-Open No.9-197527, and Japanese Patent Laid-Open No.11-190881, in which an opening is formed in part of a camera body (grip or side face), and in an opening formed in a cylindrical portion of a lens-barrel, a water-repellent microporous member such as Gore-Tex (registered trademark) and Micro-Tex (registered trademark) that allows air to pass through the opening while prohibit a water droplet to pass therethrough is provided.
To a camera body in an interchangeable lens system, however, interchangeable zoom lens-barrels having a plurality of focal-length ranges typically are attachable thereto. Accordingly, in a case where a vent for adjusting internal pressure is provided in the camera body, the vent has to correspond to a lens-barrel with the maximum change in volume, so that a considerably large water-proof or vapor resistant vent has to be provided in the camera body.
Also, in a case where the lens-barrel is provided with a water-proof vent, the appearance/aesthetics of the lens barrel may be impaired.
When a lens-barrel having large changes in volume is rapidly operated, air comes in and out through a sealing part, so that abnormal noise may be produced.
In a structure where a water-proof vent is exposed to the exterior, and a user may, under normal picture taking conditions, inadvertently touch the water-repellent microporous member while operating the camera or lens-barrel, which may result in damage to the water-repellent microstructure, such as peeling-off, or other flaws, or may result in damage in the repellency character of the water-repellent microporous member due to oil or other contaminants carried by user""s finger(s).
Also, in an arrangement in which a vent is externally exposed, as disclosed in Japanese Patent Laid-Open No.9-197527 and Japanese Patent Laid-Open No.11-190881, if water droplets cover almost the entire surface of the vent, the air volume required to be passed therethrough cannot be sufficiently maintained, whereby water/vapor may be freed to enter the interior by a vacuum pumping action. Once a droplet/vapor passes thorough the water-repellent microporous member, the water-repellent effect is extremely reduced.
It is an object of the present invention to provide a lens-barrel that moves in an optical axis direction so as to change the overall length of the lens barrel and yet is water and drip-proof (vapor-repellent) without sacrificing appearance.
In order to achieve the above-mentioned object, a lens apparatus according to a first embodiment of the present invention comprises a lens holding member that holds one of a lens and a lens group, a moving member that holds and moves the lens holding member in an optical axis direction, the moving member having a vent that provides ventilation between the interior and the exterior of the lens apparatus, a water-repellent microporous member that covers the vent, and an appearance member disposed on the moving member, with a clearance provided between the appearance member and the moving member, so as to shield the water-repellent microporous member.
In a lens apparatus according to the first embodiment, the vent may be formed on the external periphery of the moving member.
In a lens apparatus according to the first embodiment, the clearance may provide an opening in a direction opposite an object side in the optical axis direction.
In a lens apparatus according to the first embodiment, the appearance member may be a member that attaches an optical filter in front of one of the lens and the lens group.
In a lens apparatus according to the first embodiment, the vent may be a cam hole for adjusting a position of the lens holding member in the optical axis direction relative to the moving member.
In a lens apparatus according to the first embodiment, the vent may be a hole used for fixing the lens holding member to the moving member.
In a lens apparatus according to the first embodiment, a plurality of vents may be formed on the external periphery of the moving member along a circumferential direction.
A lens apparatus according to the first embodiment further may comprise a fixed member that supports the moving member for movement in the optical axis direction and a sliding member disposed between the moving member and the fixed member that closes up a clearance between the moving member and the fixed member, wherein the sliding member slides relative to the fixed member so as to allow the moving member to be displaced in the direction perpendicular to the optical axis direction during movement of the moving member in the optical axis direction.
A lens apparatus according to a second embodiment comprises a holding member that holds and moves one of a lens and a lens group in an optical axis direction, the holding member having a vent that provides ventilation between the interior and the exterior of the lens apparatus; a water-repellent microporous member that covers the vent; and an appearance member disposed on the holding member, with a clearance provided between the appearance member and the holding member, so as to shield the water-repellent microporous member.
In a lens apparatus according to the second embodiment, the vent may be formed on the face-end surface of the holding member on an object side of the lens apparatus.
In a lens apparatus according to the second embodiment, a plurality of vents may be formed along a circumference on the face-end surface of the holding member on an object side of the lens apparatus.
In a lens apparatus according to the second embodiment, the appearance member may be a ring-shaped member, and the clearance may be provided between the internal periphery of the ring-shaped appearance member and the lens.
A lens apparatus according to the second embodiment further may comprise a fixed member that supports the holding member for movement in the optical axis direction, and a sliding member disposed between the holding member and the fixed member that closes up a clearance between the holding member and the fixed member, wherein the sliding member slides relative to the fixed member so as to allow the holding member to be displaced in the direction perpendicular to the optical axis direction during movement of the holding member in the optical axis direction.
An optical instrument that obtains image information via a lens apparatus according to a third embodiment of the present invention comprises a lens holding member that holds one of a lens and a lens group; a moving member that holds and moves the lens holding member in an optical axis direction, the moving member having a vent that provides ventilation between the interior and the exterior of the lens apparatus; a water-repellent microporous member that covers the vent; and an appearance member disposed on the moving member, with a clearance provided between the appearance member and the moving member, so as to shield the water-repellent microporous member.
An optical instrument for obtaining image information via a lens apparatus according to a fourth embodiment of the present invention comprises a holding member that holds and moves one of a lens and a lens group in an optical axis direction, the holding member having a vent that provides ventilation between the interior and the exterior of the lens apparatus; a water-repellent microporous member that covers the vent hole; and an appearance member disposed in the holding member, with a clearance provided between the appearance member and the holding member, so as to shield the water-repellent microporous member.